Progress in preparation and application of short b-axis ZSM-5 molecular sieve

As one of the most widely used catalysts, the ZSM-5 molecular sieve has always been the focus of scholars’research. Due to its better diffusion performance along the b-axis straight channels compared to that along the a-axis and c-axis the zigzag channels, the control of their length plays an important role in improving the catalytic properties of molecular sieves. The main methods for controlling the anisotropic growth of ZSM-5 molecular sieves are reviewed, including structure-oriented methods and growth modification methods. The application of short b-axis ZSM-5 molecular sieves in catalytic fields such as MTP, MTH, and MTG is analyzed in detail. It is also pointed out that lamellar molecular sieves prepared with specific quaternary ammonium salts as structural directing agents have a uniform and good self-pillared structure and intercrystalline mesopores. Due to the high difficulty in preparing structural directing agents, it is more economical and environmentally friendly to partially replace quaternary ammonium salts with growth modifiers. The synthesis of specific growth modifiers is low in difficulty and cost, and the prepared molecular sieves have dispersed or agglomerated lamellar structures. The development of new processes to improve intercrystalline mesopores will enable them to have better diffusivity. The in-depth study of the precise regulation of the thickness and acidity of lamellar molecular sieves, the synthesis mechanism, and the influence of anisotropic length on catalytic performance to ensure efficient preparation of molecular sieves that take into account conversion, selectivity, and stability is of great significance to the development of short b-axis molecular sieves. © 2023 Chemical Industry Press. All rights reserved.